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Cantaloupe: Sometimes a Rough Fruit

The rind of a cantaloupe may be hard enough to knock on, but it’s not tough enough to keep out harmful pathogens, as an outbreak of Salmonella Panama reminded consumers this week. What is it that makes this melon one of the most common carriers of foodborne illness among fruits and vegetables?

Cantaloupe is particularly susceptible to contamination because it grows on the ground, where it can come into contact with bacteria from animal feces harbored in soil or rainwater runoff. However, like any fruit or vegetable, it can also pick up pathogens during harvest, handling or preparation.

Foodborne illness outbreaks from cantaloupe have been traced back to wash water, shipping ice and even contact with contaminated meat, according to a 2005 study in the International Journal of Food Microbiology.

Cantaloupe is also risky as a home for pathogens because of its unique skin. Bacteria sticks easily to the rough surface, and can even penetrate through the porous rind to the inside of the fruit.

“When it rains, [cantaloupe] could actually be sitting in water, and whatever’s in that water could actually enter inside the flesh,” says Doug Powell, professor and food safety expert at Kansas State University.

And there is one more aspect of this marbled melon that makes it more apt to cause an outbreak than other fruits: bacteria can grow on its surface after harvest. While bacteria normally cannot grow on fruits or vegetables after they are picked due to a lack of moisture and nutrients, E. coli has been shown to multiply on the surface of cantaloupe and watermelon, according to an FDA article on fresh produce safety.

If not washed off the melon, bacteria can travel from the exterior to the edible part in a number of ways. Aside from permeating the rind itself, bacteria can be transferred when a person handles a husk carrying germs and then touches the fruit. It can also travel on the knife as the fruit is cut, according to the 2005 study.

Even a small amount of bacteria can be dangerous if it reaches the inside of the cantaloupe, because once there it can increase. The FDA Food Code cites cut melon as a potentially hazardous food, since its low acidity and high water content make it capable of supporting bacteria growth.

Just how risky is it to eat cantaloupe? “Cantaloupe’s always in the top five of fresh fruits and vegetables for outbreaks,” says Powell.

Indeed there have been at least five outbreaks linked to cantaloupe in the past five years alone, according to outbreakdatabase.com.

In 2001, out of a sample of 151 imported cantaloupes, the FDA isolated Salmonella from eight (5.3 percent), and Shigella from three (2 percent). Foreign cantaloupe has historically been responsible for the majority of foodborne illnesses associated with that fruit.

But outside the realm of fresh produce, cantaloupe remains relatively low on the list of overall foodborne risks. Overall, produce accounts for 13 percent of foodborne illness outbreaks, according to a report from the Center for Science in the Public Interest (CSPI).

And to reduce the risk of foodborne illness from cantaloupe even further, consumers can take precautionary steps when preparing and eating it. These include:

— cleaning knives and cutting boards after cutting cantaloupe open, before scooping out the flesh

— washing hands thoroughly after handling the exterior of the melon, before touching the edible part

Opinions are mixed as to whether washing cantaloupe helps reduce the risk of illness. According to the 2005 study, washing melon in running fresh water produced a significant reduction in bacteria, as did soaking the melon in chlorine. However, soaking melon in water made contamination worse, as it allowed bacteria to survive and even to travel from one melon to another.

If consumers choose to wash melon, they should be advised that bacteria can splash onto surrounding surfaces, and should be sure to clean these before next preparing food on them.

The problem of contamination and potential growth of bacteria on melons is a difficult one. Normally with a product that bacteria can both harbor and grow in we would require that the items be kept under temperature control, the FDA food code requires cut melons to be held at 41 degrees until service for example.
Prior to cutting (processing) there are no current provisions for limiting growth of bacteria on melons. Food safety with melons and most raw agricultural products is a matter of contamination control. Melons may or may not be washed in the packinghouse to remove contamination before shipping to retailers. Again, no mandatory provisions exist for any type of post-harvest treatment with melons. Thus, the consumer or end user becomes the main focus of prevention, especially for melons.
The challenges for the fresh produce industry are in identifying the risks in the growing, harvesting, packing and shipping of these items, and then taking a combination of preventive measures that reduces those risks to the consumer to some measurable level. The new research pointed out here is useful, but the response will take some time, given the nature of the industry and what it has traditionally seen as risk.
Framers know that wild animals are a major concern in melon operations; they consume and destroy a significant amount of crops. Deer, pigs, raccoons, as well as birds are attracted to these growing and harvesting areas. While growers may not have absolute control over access to the growing areas, harvesting methods must account for contamination found. Operations under third party standards are required to monitor for these hazards and not harvest areas with obvious signs of animal intrusion. That procedure if rigorously done limits the wide scale fecal contamination problem but does not eliminate it. Handling thereafter must be sanitary. Packers that do not wash melons can do little to remove contamination.
Buyers drive this model, and many will accept raw agricultural products that have not had a washing step, leaving the consumer as the first line of defense.
However, washing when it can be accomplished in a large packinghouse is itself hazardous. During washing, if antimicrobial quality of wash water is not maintained, water becomes a vehicle to further spread contamination between lots. Diligent control of wash water quality is often a critical control in a food safety program for this reason.
We may not be able to eliminate the pathogens in melons at any one stage of the production system, thus calling for a coordinated effort between growers, handlers, shippers and end users. We need to strengthen the weak links in this chain to the extent we can, and combine that effort with effective microbiological testing and recall procedures and oversight.
The regulation of the supply chain for agricultural products in general is very weak at present, but we expect this situation to change soon. Efforts to properly guide the fresh produce industry and enforce necessary public health controls will improve as the new federal policies and procedures come into effect.
An expansion of the regulatory controls and industry led efforts will eventually reduce the risk of contamination in raw agricultural products overall, but don’t expect immediate resolution of the fundamental problems of melons, and perhaps, other high risk produce items.
Thanks for informing the consumer about safe handling, as the fresh produce industry continues to make progress in reducing risks to end users.

Minkpuppy

I’m acquainted with a food microbiologist at Texas A&M through a food micro class I took there a few years ago. During one of his lectures, he mentioned that several years ago he was helping to investigate an outbreak in melons (think it was in the Rio Grande Valley but my memory fails me) that was believed to have been caused by using contaminated irrigation water.
While walking the fields, he noticed several snakes scurrying out of the way. He strongly believes the snakes’ presence also contributed to the outbreak. Reptiles are known to harbor Salmonella and he said the field was full of them. I don’t recall if they caught and tested any of the snakes.
Even though the details are hazy, this story has stuck with me all these years. Just goes to show that some outbreaks may have multiple sources, even ones you wouldn’t think of, like snakes.

Anthony Boutard

The netted musk melons sold as cantaloupes slip when they are ripe. If you look at the melon in the photo, you can see the bright green area that is called the abscission zone. I believe this is why musk melons are particularly vulnerable to contamination. This is the vascular zone through which the fruit was constructed. It is a highway into the tissues of the melon. When this area is fresh, care must be taken to keep it clean and dry. Osmosis will quickly draw contaminated water into the fruit.
When we harvest musk melons, we never wash them. If there is some soil clinging to the fruit, we remove it with a clean dry towel, keeping the scar at the top. Putting melons in any sort of water bath or pressure washing is asking for problems, especially immediately after harvest. Pick them dry and keep them dry. Within a few hours, the abscission zone dries and seals the melon. Refrigeration delays this process.
Melons should be drip irrigated to keep them clean. But as someone who grows the melons commercially, I believe the contamination hazard is due to post-harvest handling. If the fruit remains dry from harvest through sale, and the abscission zone remains clean, the risks should be small.
Anthony Boutard
Ayers Creek Farm

khushi sahu

You have written like a pragraph but nice Anthony Boutard we can learn more things.